1. Field of the Invention
Methods and apparatuses consistent with the present invention relate to digital rights management, and more particularly, to digital rights management in which a user can use purchased content flexibly regardless of device while safely protecting digital rights.
2. Description of the Related Art
Research on digital rights management (DRM) is being actively conducted, and commercial services using DRM have been introduced and are being prepared to be introduced. DRM is a technological concept for protecting digital content which can be easily copied and distributed.
There have been efforts to protect digital content, but related art technologies have focused on preventing unauthorized access to digital content. For example, access to digital content has been allowed only to users who paid for the content. However, digital content can be easily re-used, processed, copied, and distributed. Hence, when a paying user copies and distributes the content without permission, users who did not pay for the content can use the digital content.
In order to solve this problem, digital content needs to be encrypted before being distributed, and there should be a license, called a Rights Object (RO), in order to use the encrypted digital content. Hence, a device intending to use content should store the RO, or communicate with another device having the RO. Further, if the RO exists with content in an integrated form, the content cannot be used by other devices exempting the device storing the content. Content and ROs can be copied and moved between devices, but there are constraints for copying and moving (for example, moving more than a predetermined number of times can be prohibited).
Korean Unexamined Patent 10-2005-0045883 (Content-Sharing System, Content-Processing Device, Information-Processing Device, Program, Recording Medium, and Content-Sharing Method) discloses a technology that can share content between devices while protecting digital rights by adding the source ID, which specifies a device that provides content, to the content, and by providing a device having a replay-permission-ID list that includes the source ID added to the content. However, according to Korean Unexamined Patent 10-2005-0045883, content should be directly transmitted between devices in order to share content. Hence, movability of content can be restrained depending on the storage capacity of a device receiving content, and content cannot be shared between devices that cannot communicate with each other, both of which are problems.
Therefore, there is a need for a technology, by which a user can use purchased content flexibly regardless of the device while safely protecting digital rights.